Oscillograph apparatus



April 5, 1960 H. l. CHAMBERS ET AL 2,931,690

OSCILLOGRAPHAPPARATUS Filed June 21, 1956 w fmh M A TTORNEVS uite d States Patent OSCILLOGRAPH APPARATUS Herbert 1. Chambers and Albert W. Fischer, Pasadena, Kauno E. Sihvonen, Arcadia, and Gardner P. Wilson, Pasadena, Calif., assignors to Consolidated Electrodvnamics Corporation, Pasadena, Calif., a corporation of California Application June21, 1956, Serial No. 592,764

7 Claims. (Cl. 34674) This invention provides an improvement in direct recording oscillograph apparatus.

In a typical direct recording oscillograph, an elongated string or conductor is disposed to extend transversely to a magnetic flux and is adapted to move transversely in response to an applied electric signal. A recording medium such as current-sensitive paper is arranged to slide over an anvil or knife edge past the conductor, which is perpendicular to the anvil edge and contacts the paper at the intersection of the conductor and the anvil edge. Means are provided for applying the signal to the conductor to cause it to vibrate within the magnetic field and slide back and forth on the paper as the paper is pulled past the conductor. Means are also provided for passing current between the paper and the conductor so that the paper is marked at the point of contact between the string and the paper. Thus as a varying signal is applied to the conductor, it moves laterally of its longitudinal axis and slides over the surface of the paper, leaving a mark or trace on the paper representative of the strength and frequency of the signal.

One difliculty with the above described system is that for low frequency or slowly changing D.C. signals, the conductor tends to stick intermittently on the paper, giving rise to erroneous recordings and traces which are erratic. This invention provides apparatusfor avoiding that difiiculty by reducing the contact friction between the conductor and the paper without appreciable deterioration of the writing trace. This is accomplished by causing the conductor to vibrate longitudinally at a small amplitude and at a relatively high frequency, resulting in a decrease of contact friction between the conductor and the paper.

Briefly, the invention contemplates oscillograph apparatus for recording a signal. The apparatus includes means for producing a magnetic field and an elongated movable conductor which is supported to extend transverse to the direction of the magnetic field. A recording medium is adapted to make point contact with the conductor and be removed with respect to the conductor. Means are provided for applying a signal to the conductor and for causing the recording medium to be marked where it is in contact with the conductor. Means are also provided for vibrating the conductor longitudinally.

In the preferred form of the invention the conductor is supported at one end by a spring which will permit the conductor to be displaced longitudinally, and the other end of the conductor is supported on an armature which is vibrated longitudinally with respect to the conductor by means of an alternating current electromagnet.

These and other aspects of the invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic elevation of oscillograph apparatus employing the invention; and

2,931,690 Patented Apr. 5, 1960 Fig. 2 is a schematic view taken on line 2-2 of Fig. 1 showing in detail an electromagnet adapted to vibrate the conductor longitudinally.

Referring to the drawing, the string element is a flexible elongated conductor 10 which is supported at its right hand end (as viewed in the figures) by a cantilever spring 12 and at its other end by an armature 13 connected to a U-shaped alternating electromagnet 14. A conductive bearing sleeve 15 of ferro-magnetic material is coaxially disposed around and attached to the center of the string.

, The spring is attached at one end to the inner end of a platform 16 which is in turn attached at its outer end to one of the upright sides of a U-shaped magnetic yoke 20. The electromagnet is mounted on a second platform 21 attached to the other upright of the yoke. Both platforms are of a suitable insulating material so that the string is electrically insulated from the yoke.

The magnet yoke supports an upper pole piece 22 which includes right and left (as viewed in Fig. 1) upper pole members 23, 24 respectively. The upper pole members are colinear and spaced apart. A writing anvil 25 is mounted between the upper pole members and has an elongated bottom edge 26 contoured to permit the smooth passage of a strip of current-sensitive recording paper 27 over it between the upper pole member and in direct contact with the bearing sleeve on the string.

The paper moves from a supply reel 29 to a take up reel 30 over guide rollers 31. The reels are powered by suitable means (not shown). The anvil edge is perpendicular to the string and supports the paper for a distance slightly greater than the maximum transverse amplitude of the string.

A lower pole piece 32 is located directly below and spaced from the upper pole members to form a magnetic gap"f -3 between the upper and lower pole pieces. The string is disposed in the gap and is perpendicular to the magnetic flux between the upper and lower pole pieces, which are connected by the yoke. The sleeve is magnetically attracted toward the anvil and maintains the proper writing pressure against the paper.

Writing current is supplied to the current-sensitive paper from a battery 35 which is connected through a limiting resistor 36 to brushes 37 in contact with the sensitive side of the paper. Current passes from the brushes through the current-sensitive surface of the paper to the string.' The current density at the point of contact between the string and the paper is sufficiently high to cause the paper to be marked. The string receives a signal to be recorded from a signal source 38.

Referring to Fig. 2, the spring 12'13 perpendicular to the magnetic flux and to the longitudinal axis of the conductor. The armature is connected at one end to one end of the U-shaped alternating current electromagnet, and the other, which is free, supports one end-of the string. The armature has sufficient flexibility to vibrate at a relatively high frequency. A suitable source 40 of high frequency current is adapted to supply an alternating magnetic flux between the armature and the electromagnet to cause the armature to vibrate and impart a small amplitude, high frequency vibration to the string.

The operation of the apparatus is as follows:

The supply and take up reels are turned on to move the recording paper past the anvil, and a signal is applied to the string. As the signal changes, the string moves transversely of its longitudinal axis. Alternating current is supplied to the electromagnet to cause the armature to vibrate the string longitudinally. Preferably the frequency of the alternating current is equal to the resonate frequency of the armature and string assembly to keep the input of energy to a minimum. Current from the writing source causes a mark to be made on the recording paper at the point of contact traced by the string on the paper. The longitudinal vibrations of the string and sleeve reduce the contact friction between the paper and the string, and results in a trace which accurately reflects the signal applied to the string, even though the signal changes very slowly.

We claim:

1. Oscillograph apparatus for recording a signal, the apparatus comprising means for producing a magnetic field, an elongated movable conductor, means for supporting the conductor to extend transverse to the direction of the magnetic field, a flexible recording medium,

means for imparting a relatively sharp curvature to the surface of a portion of the recording medium along a line transverse to the movable conductor, means for urging the conductor into contact with the curved surface of the recording medium, means for moving the recording me-. dium with respect to the conductor, means for causing the recording medium to be marked where it is in contact with the conductor, and means for vibrating the conductor longitudinally.

2. Oscillograph apparatus for recording a signal, the apparatus comprising means for producing a magnetic field, an elongated movable conductor, means for sup porting the conductor to extend transverse to the direction of the magnetic field, a flexible recording medium, means for imparting a relatively sharp curvature to the surface of a portion of the recording medium along a line transverse to the movable conductor, means for urging the conductor into contact with the curved surface of the recording medium, means for moving the recording medium with respect to the conductor, means for causing the recording medium to be marked where it is in contact with the conductor, means for applying the signal to the conductor, and means attached to the conductor for vibrating it longitudinally.

3. Oscillograph apparatusfor recording a signal, the apparatus comprising means for producing a magnetic field, an elongated movable conductor, means for supporting the conductor to extend transverse to the direction of the magnetic field, a flexible recording medium, means for imparting a relatively sharp curvature to the surface of a portion of the recording medium along a line transverse to the movable conductor, means for urging the conductor into contact with the curved surface of the recording medium, means for moving the recording medium with respect to the conductor, means for causing the recording medium to be marked where it is in contact with the conductor, means for applying the signal to the conductor, and means attached to one end of the conductor for vibrating it longitudinally.

4. Oscillograph apparatus for recording a signal, the apparatus comprising means for producing a magnetic field, an elongated movable conductor, a spring supporting the conductor at one end to permit the conductor to move longitudinally, means for supporting the other end of the conductor so the conductor extends transverse to the direction of the magnetic field, a flexible recording medium, means for imparting a relatively sharp curvature to the surface of a portion of the recording medium along a line transverse to the movable conductor, means for urging the conductor into contact with the curved surface of the recording medium, means for moving the recording medium with respect to the conductor, means for causing the recording medium to be marked where it is in contact with the conductor, means for ap plying the signal to the conductor, and means for vibrating the conductor longitudinally.

5. Oscillograph apparatus for recording a signal, the apparatus comprising means for producing a magnetic field, an elongated movable conductor, means for supporting the conductor to extend transverse to the direction of the magnetic field, a recording medium in contact with the conductor, means for moving the recording me dium with respect to the conductor, means for causing the recording medium to be marked where it is in contact with the conductor, means for applying the signal to the conductor, an armature attached to the conductor, and means for vibrating the armature longitudinally with respect to the conductor.

6. Apparatus according to claim 5 which includes means for supporting the conductor at one end to permit longitudinal deflection of the conductor, and means connecting the armature to the opposite end of the string.

7. Apparatus according to claim 5 in which the means for vibrating the armature is an alternating current elec tromagnet.

References Cited in the file of this patent V UNITED STATES PATENTS 1,958,696 

